mypros+
Error code reference

Thermador Oven Error Code F40

Upper meat probe shorted.

Thermador codesThermador oven codes

Upper meat probe shorted.

First step from the service manual

Check meat probe wiring at pin header P2 on display head.

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

MyPros+ Max

Get the full diagnostic procedure for F40.

  • Step-by-step tests with expected resistance, voltage, and continuity values
  • Wiring diagram references and connector pinouts from the OEM service manual
  • Verified part numbers when replacement is required
Get the full procedure

$29/month · Cancel anytime · Or $9.95 3-day pass

What F40 means on a Thermador oven

The F40 error code on a Thermador oven indicates that the upper meat probe circuit has detected a short condition. A short in this context means the resistance across the probe's thermistor circuit has dropped to an abnormally low level, signaling to the control board that the probe wires are making unintended contact with each other or with a grounded surface. The oven's control system continuously monitors the meat probe's resistance to calculate internal food temperature, and when the resistance falls outside the expected range, the F40 fault is triggered and cooking is halted.

The diagnostic process begins at pin header P2 on the display head, which is the termination point for the upper meat probe wiring harness. This connector is the most likely point of failure because it is subject to repeated insertion and removal cycles, heat exposure, and occasional moisture. Technicians should inspect P2 for bent or corroded pins, damaged insulation on the wiring harness leads, and any visible signs of melted or pinched wiring between the probe jack and the display head.

Beyond the connector itself, the fault can originate at the probe jack mounted inside the oven cavity, along the wiring harness routing path, or within the meat probe accessory itself. A damaged probe with internally shorted wires is a common culprit, especially if the probe has been pinched under a rack or exposed to high direct heat. Resistance across a healthy meat probe thermistor should fall within the manufacturer's specified range at room temperature, and any reading near zero ohms confirms a short condition in the probe or its circuit.

Source: manufacturer service documentation.

Common causes of F40

  1. 01

    Damaged or faulty meat probe

    Part replacement

    The meat probe thermistor can short internally if the probe has been crimped under an oven rack, dropped, or exposed to direct flame. Test the probe with a multimeter at room temperature; a near-zero ohm reading confirms an internal short.

  2. 02

    Loose or corroded connection at pin header P2

    Wiring / connection

    The wiring harness connector at P2 on the display head is the first inspection point. Corrosion, bent pins, or a loose seating of the connector can cause a short circuit condition that triggers F40.

  3. 03

    Damaged wiring harness between probe jack and display head

    Part replacement

    The wiring running from the meat probe jack inside the oven cavity to the display head can be pinched, chafed, or melted by heat exposure, causing the two conductors to contact each other and create a short.

  4. 04

    Faulty meat probe jack inside the oven cavity

    Part replacement

    The socket where the probe plugs into the oven wall can accumulate grease and debris or suffer heat damage that causes internal pin contact. Inspect the jack for visible contamination or physical damage.

  5. 05

    Failed display head control board

    Part replacement

    If the probe, harness, and jack all test correctly, the display head board itself may have a failed input circuit that falsely reports a short condition. This is the least common cause and should be diagnosed after all other components are cleared.

See the test procedure for each cause

Frequently asked questions about F40

What does F40 mean on a Thermador oven?
F40 on a Thermador oven means the control system has detected a short circuit in the upper meat probe circuit. The oven monitors the resistance of the probe's thermistor to track food temperature, and when that resistance drops to an abnormally low level, the F40 fault is triggered. The error points to a problem with the probe itself, its wiring harness, or the connector at pin header P2 on the display head.
Can I fix the F40 error myself, or do I need a technician?
Some causes of F40 are DIY-friendly. Start by unplugging any meat probe from the oven and power-cycling the unit to see if the code clears, which would point to a faulty probe accessory that simply needs replacement. Inspecting and reseating the wiring connector at P2 on the display head is also within reach for someone comfortable working with appliance wiring. However, replacing internal wiring harnesses or the display head board typically requires a qualified technician.
Is it safe to use my Thermador oven when the F40 error is showing?
The F40 fault is specific to the meat probe circuit and does not necessarily indicate a hazard with the main oven heating system. However, the oven will typically halt or restrict operation when an active fault code is present. It is best not to attempt to bypass the fault and to resolve the underlying issue before resuming normal use, particularly if any wiring damage is suspected.
Will resetting the oven clear the F40 error code?
A power reset, such as switching off the circuit breaker for 30 seconds and restoring power, may temporarily clear the F40 code if the fault condition is intermittent. However, if the underlying short in the probe or wiring remains, the code will return as soon as the oven's control system performs its next diagnostic check. A permanent fix requires identifying and correcting the faulty component.
How much does it cost to repair a Thermador oven F40 error?
Repair costs vary depending on the root cause. A replacement meat probe accessory is typically the least expensive fix, generally ranging from $30 to $80. A wiring harness replacement or probe jack repair with a service call can run from $150 to $350 depending on labor rates and parts. Replacing the display head control board represents the most expensive scenario, potentially ranging from $300 to $600 or more including parts and labor.

Related Thermador oven codes

All Thermador oven codes
View all 103 Thermador oven codes

78,000+ service manuals · 160,000+ error codes · 55+ brands

Get Started

$29/month · Cancel anytime · Or $9.95 3-day pass